Diane 35 and TSH Levels
Direct Answer
There is no evidence that long-term use of Diane 35 (cyproterone acetate and ethinyl estradiol) lowers TSH levels. The available research on Diane 35 focuses on its effects on sex hormones, ovarian function, and androgenic symptoms, with no documented impact on thyroid-stimulating hormone.
Evidence Review
Hormonal Effects of Diane 35
The documented hormonal changes from Diane 35 use include:
- Suppression of gonadotropins (LH and FSH) with significant decreases in the LH/FSH ratio occurring after 3 cycles of treatment 1
- Reduction in androgens including total testosterone (39% decrease), free testosterone (62% decrease), androstenedione, and DHEA-S levels 2, 1
- Marked increase in sex hormone-binding globulin (SHBG) by approximately 3-fold during treatment cycles, which persists throughout therapy 2, 1
- Modest increases in prolactin levels with an increasing tendency during treatment 3
Absence of Thyroid Effects
- No thyroid hormone alterations documented: Multiple pharmacokinetic and hormonal studies of Diane 35 measured comprehensive hormone panels including LH, FSH, prolactin, estrogens, progesterone, and various androgens, but none reported changes in TSH, T3, or T4 levels 3, 2, 1
- No clinical thyroid symptoms reported: Studies tracking side effects over treatment periods of 9-30 cycles documented weight gain, breast tenderness, mood changes, and blood pressure increases, but no thyroid-related symptoms 1
Important Distinction: Estrogen Effects on Thyroid Function
While Diane 35 does not lower TSH, it's important to understand that:
- Estrogen-containing medications increase SHBG and thyroxine-binding globulin (TBG), which can affect total thyroid hormone levels but typically does not change TSH in euthyroid individuals 4
- Patients with pre-existing hypothyroidism on levothyroxine may require dose adjustments when starting estrogen-containing contraceptives due to increased binding proteins, but this represents increased thyroid hormone requirements, not TSH suppression 4
Clinical Implications
- TSH monitoring is not required specifically for Diane 35 use in women without pre-existing thyroid disease 3, 1
- If TSH abnormalities occur in a patient taking Diane 35, investigate other causes of thyroid dysfunction rather than attributing it to the medication 5
- For patients with hypothyroidism on levothyroxine, monitor TSH 6-8 weeks after starting Diane 35, as increased binding proteins may necessitate levothyroxine dose increases, but this is distinct from Diane 35 lowering TSH 6, 4